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Spark plugs black and they smell of gas


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So I've been tinkering with my "NEW ride" (1985 Honda Shadow VT500C) - Ok stop laughing, I know "how can 1985 and NEW be in the same post let alone the same sentence".


Anyway just a few issues ....


The 2 that have me most concerned are:


1. The spark plugs (ones that came in the bike from previous owner) - They are black (sooty) and a little wet and smell of gas.

My first thought is I'm glad it's gas and not oil, I think that would be worse (piston rings not doing their job etc.) although it might still be a problem I'm going to hate to hear the answer to. Also to add to this nothing was melted or shorted or cracked etc. even the gap was still good, just the black and gas.


So I got two new Honda plugs (I know it has four, but I'm not ready to take off the seat and tank yet, so two is what I can access easily) from local dealer, gapped them, installed them and fired up the beast. I let it run about 30 minutes (solid on the temp gage, fully warmed) I then shut it down and waited a couple of hours, removed the new plugs and inspected them. The result was that they were a little black, not as bad but black for sure as opposed to light brown or white (30 minutes vs. whole season of riding by the previous owner, I assume if I do nothing my new ones will look like the others in a matter of days once riding etc.) and wet and smelt of gas (so I ruled out plug just not firing) I also checked it for spark by connecting the plug and holding it against the fins, spark seemed ok (but what do I know) BTW: both front and rear cylinder have this issue.


bike seems to run good, no back firing or hesitation etc. even with this condition, but I have fears it may be something much worse. so the INTERWEB tells me that it's running too rich, great to know ..... no idea what to do about it, but I have gotten this far (and FYI I'm a computer guy not a mechanic :)) so this is kinda new to me.


2. The second issue that has me worried is that at idle (900-1100 RPM) there is a VERY NOTICIBLE knocking or ticking. As soon as you touch the throttle it stops, if I increase the idle either via the choke or using the idle control screw (2k-3k RPM) it again stops. Again not being very mechanically inclined I'm figuring this might be a valve ??? not sure though. I also have a suspicious feeling that this valve issue might also be causing problem number 1 above. again just guessing at this point.



I just got the bike last week so as you all know (weather being what it is)..... I have no idea how it drives at this point, I can tell you that on the centre stand with rear wheel off the ground, I was able to shift through all 6 gears, and it seemed to shift smooth through all 6, but again without a load who knows. I also have played around in the garage, just finding the friction zone etc. clutch seems nice and friendly.


I also installed the terminals for the Battery Tender Jr. and have it hooked up using the quick disconnect (amazing how cranking the bike after sitting a couple of days at -15c or so can DRAIN THE BATTERY SO FAST) no prob. though just jumped it off my car (with car not running of course) fired after a few tries, once warm fires one shot no hesitation and without the jump cables. :)


I'm getting ready to put it back to sleep till riding season, but thought I should maybe address these issues before closing it down. The previous owner does have seafoam in with the gas right now and it is still 95% full (will top it off when putting it to bed) I wanted to put a teaspoon of oil in each cylinder and let it go back to sleep with it's little tender plugged in, But seeing as I have not done that I thought it might be a good idea to correct anything major before doing so. Would hate for riding season to start and there I am fixing instead of riding. I also have to try and attempt this on my own as taking it in to the shop and saying "here fix it" IS NOT AN OPTION. unless A B S O L U T E L Y  necessary. I'm also limited by tools, but I do have the Honda Service manual, the Clymer Service manual, and get this THE ORIGINAL OWNERS MANUAL after 29 years, it's pretty cool to get that with the bike, would be very hard to find I imagine (came close to losing it, fell between the seats of the U-Haul, went back 3 days later. BAM right there between the seats. Did I mention I'm very LUCKY. Darn the bike even came with one of those little evil spirit wards (bell) hanging off some pin on the rear axle :)



Anywho any help or advice would be much appreciated.


And sorry about killing 20 minutes of your life by reading this (toooooooo long of a) post :)



Cheers and thanks

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In the Clymer Manual it suggests that fouled plugs could also be the result of letting the bike IDLE too long ...


Well again as the weather is in charge at the moment, IDLE is all I can do, and I admit I have let it idle a few times for 20 minutes or more  :(




I think I'm just going to put it bed and when the nice weather hits, take it out for a 20-30 Km burn, back to my garage and drop a couple new plugs in it and take it out for good 50-100 Km ride.


Hopefully at that point the plugs will exhibit better behavior, and my "running rich" issue will be no more (God willing).



Ah heck, I just want to get some time on 2 wheels, and this bike will get the job done.


When I took it in for the safety everyone who saw it says it looks great for it's age. After 1 rear tire and rear drum pads - bike has a valid safety cert and is just awaiting plates and insurance (and yes I know the cert is only good for 36 days).


Thanks again guys   

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In my experience Black fouled plugs ... Check your Choke (if equippped) ensure its not slightly engaged

Second Check your Airfiter is Clean,


the old ones may have been providing a weakend spark for sometime resualting in the back gassy plug


You need to definately not idle that bike.... Sitting on the side stand idling is the number one cause of premature ware from

low lubercation especially if the pre owner didn't do the oil change often enough


my advice,.. NGK plugs new air filter, Carb cleaner in the next 3 tanks of gas,.....


And to everyone out there,... I know its a pain but you should NEVER let your bike Idle on the side stand

especially air cooled ones,.... always up right


the tick at idle may be excessive ware caused by letting her idle on the side stand starving the throttle side top end


Seen it many times even on liquid cooled Race bikes


Just my two cents

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Cool thanks Sir


I have not used the side stand just the centre stand and it's water cooled.


The bike was put away for the winter before I got it, but taking it in and doing the safety "cracked that seal" (when the guy from the shop dropped it off he started it) and had it running while we walked it into my garage. So I figured meh, I'll run it a couple of times and put it back to sleep. which I have done now.


Dropped a tablespoon of 10w40 in each cylinder, replaced the plugs, put the tender jr. on it, covered it up.

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  • 3 weeks later...

i am fortunate to have a heated garage so i fire my bike as well as the wives about once a month takin my carbs off to clean is a big project so i find i have no issues this way. i would change all the plug clean or change the air cleaner and run some sort of carb cleaner in it for a cpl tanks then take plugs out again then u have to decide if it is running a bit rich but doesn't seem to cause prob like stalling or hard to start or flooding i would hesitate to change it if u lean it out to much u run the risk off engine damage or failure remember lean is hot rich is cool  i have a honda vtx 1300 and the wives is a honda 750 c2 shadow booth have been piped and rejetted  the plugs are a bit black but have no run issues so i just leave it  hope this helps 

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